Schistosomiasis has been described as "one of the most devastating diseases of mankind, second only to malaria in it's deleterious effects on the social & economic development of populations in many warm areas of the world". The disease is world-wide & is estimated to affect more than 300 million people. The overall general objective of this research is two- fold: 1) to study the biology of the nervous system of Schistosoma mansoni miracidia; & 2) to study the host-parasite relationships of miracidia & snail hosts. The nervous system of schistosome miracidia is well- developed, yet poorly understood. The PI has carried out extensive baseline studies on schistosome miracidia & snail hosts that are relevant & pertinent to the proposed research. Part I of this project is designed to investigate "putative" neurotransmitter substances & enzymes in schistosome miracidia. We intend to continue to study the neurons that are serotonergic, determine neuron site(s) that are dopaminergic, norepinergic & cholinergic in schistosome miracidia; their central, peripheral & terminal fields of arborization & the localization site(s) for the neurotrans. enz. acetylcholinesterase using enz. marker choline acetyltransferase and STD. methods. Such data on the nervous system of miracidia should provide insight(s) & lead to experiments on the role(s) of these "putative" substances. Studies on serotoner., dopaminer., norepiner. and choliner. systems in the miracidia will thus lead to experiments on mechanisms for determining neurotrans., no., type, concentrat., affinity & binding; in addition to the use of specific neuroantagonists & agonists for experimental manipulation of this system. Part II of this research is to investigate kinetic enzyme activities, localization site(s) & mechanisms of host-parasite interactions. We plan to localize several hydrolytic enzymes in susceptible & non-susceptible snail hosts (i.e., Biomphalaria sp.); & to investigate kinetic alterations in the levels of some hydrol. enz. following S. mansoni infection. Such data will provide leads and insight on the identification, distribution & possible role(s) of hydrol. enz. in susceptible & non-susceptible snail hosts. Such data will also contribute toward our better understanding the metabolism of these enz. in snail hosts; the physiology of host-parasite relationships & shed some knowledge on cellular defense responses. The methods of approach for this project include a combination of morphological & biochemical procedures. Light microscopy histochemistry, fluorescent immunohistochemistry, EM cytochemistry & enzyme assays.